1. Field of the Invention
The present invention relates to a part transfer apparatus, and more particularly, to an apparatus for aligning and intermittently conveying parts.
2. Description of the Related Art
Hitherto, small parts, such as chip parts, have been transferred by, for example, a method in which parts are caused to slide down along a downwardly inclined groove for guiding parts by using potential energy, a method in which parts are fed by air pressure using compressed air or negative pressure, or a method in which an endless belt that forms a bottom face of a groove for conveyance is intermittently driven (e.g., Japanese Unexamined Patent Publication No. 8-48419).
The slide-down method has low reliability because parts are sometimes caught during travel due to contaminants thereon or static electricity. Although the air method simplifies the structure, it is sensitive to pressure changes. Furthermore, since an air pressure source is required, the cost is increased. In contrast, the belt drive method has a relatively high reliability, whereas a drive mechanism for intermittently driving the belt is complicated, and durability is apt to be lowered.
Accordingly, the present inventors have proposed a transfer apparatus that does not significantly damage parts and that provides high reliability and a simple structure (Japanese Patent Application No. 10-111671). The Japanese Patent Application No. 10-111671 has not been published yet. This transfer apparatus comprises a guide groove for aligning and transferring parts, a conveyor member placed at the bottom of the guide groove so as to move forward and backward in the direction of the groove, and a driving means for reciprocally driving the conveyor member so that the reverse speed of the conveyor member is higher than the advance speed, and the transfer apparatus conveys parts by using the difference in frictional force.
In such a transfer apparatus, a cam that is turned in one direction is provided as the driving means, a spring is provided to urge the conveyor member backward, and the rear end of the conveyor member is made to contact the peripheral surface of the cam, whereby the conveyor member can be reciprocally driven on the above-described condition. In this case, the structure of the driving means is substantially simplified, and the motion of the conveyor member can be freely set by changing the cam curve.
Since the cam and the conveyor member are in direct contact with each other, however, the force perpendicular to the moving direction of the conveyor member acts on the conveyor member, thereby vibrating the conveyor member vertically. This vibration lifts parts placed on the conveyor member, and thereby impairs transfer efficiency. Furthermore, since the amount of sliding between the peripheral surface of the cam and the conveyor member is large, and the conveyor member is pressed against the peripheral surface of the cam by the spring, both the members may undergo serious wear.